Apparatus for measuring force or load by the use of vibratory beams are well known. In such apparatus a vibratory beam is excited and vibrates at particular frequencies related to the amount of stress applied to the vibratory beam. Frequency of vibration is also dependent upon the stiffness of the beam. Such apparatus provide substantial advantages in that construction is simple and analogue-to-digital converters are not required because a digital value is directly produced in such apparatus.
In my U.S. Pat. No. 4,734,931 disclose force measuring apparatus wherein mechanical Q is high so that oscillations can be maintained in the vibratory beam whereby smaller sources of external energy are required to excite the beam. In my aforesaid patent the force measuring apparatus comprises a vibratory beam which vibrates back and forth at a measurement frequency and which includes a rotational mass coupled to the beam at an internal nodal point which does not vibrate back and forth at the measurement frequency but wherein the rotational mass rotates at the measurement frequency.